You could definitely fit 2-3 shrimp, maybe even a couple more. However, Corys prefer shoals and like groups of 5 or more....you could probably get away with that many if you kept to 6 females though. Ottos you shouldn't add unless you have a big algae problem, they can be picky eaters and won't always accept prepared foods.
You want to stay away from guppies....they'll breed like mad if you get both genders, have a high bio-load(poop a lot), and its very likely your girls will nip them to death.
On another note, you don't need fish or other creatures to 'help cycle'. In fact, cycling with fish or other creatures can be rather cruel on them and even have deadly effects if not done properly.....and I've read shrimp are delicate, they should only be added after your tank is pretty well established....and I KNOW ADFs, Corys, and Ottos are all sensitive and should never be added to a new tank. Here is a topic that explains the cycling process pretty well: http://www.tropicalfishkeeping.com/f...ium-cycle-252/
Here is a thread that explains how to safely cycle with fish, if your up to the challenge: http://www.bettafish.com/showthread....ght=Cycle+Fish
If not, google 'Fishless Nitrogen cycle' and read up on as many links as you can.
(No matter want though, you'll want to pick up a freshwater liquid dropper test kit, the API brand is a really good one, before you begin anything)